Brushless motor starting method and control device

Abstract

For starting a three-phase four-pole sensorless brushless motor including a stator having three-phase coils and a four-pole magnet rotor provided in correspondence with the stator, it is arranged to energize any two-phase coils of the three-phase coils in a predetermined energizing sequence; monitor magnetic flux generated in the other one-phase coil; and switch the two-phase coils according to a specific case where the monitored magnetic flux changes to a positive or negative side and in mid-course further changes to an opposite side. For instance, when the specific case is a case where the magnetic flux monitored by first energization changes to the negative side and in mid-course further changes to the positive side, the first energization is immediately stopped and switched to fourth energization by skipping two energizations in the predetermined energizing sequence.

1 . A starting method for starting a three-phase four-pole sensorless brushless motor including a stator having three-phase coils and a four-pole magnet rotor provided in correspondence with the stator, the method comprising the steps of:
 energizing any two-phase coils of the three-phase coils in a predetermined energizing sequence for starting of the brushless motor;   monitoring magnetic flux generated in the other one-phase coil; and   switching energization to the two-phase coils according to a specific case where the monitored magnetic flux changes to a positive or negative side and in mid-course further changes to an opposite side.   
     
     
         2 . The starting method of the brushless motor according to  claim 1 , wherein
 when the specific case is a case where the magnetic flux monitored by first energization changes to the negative side and in mid-course changes to the positive side, the first energization is immediately stopped and switched to sixth energization by skipping four energizations in the predetermined energizing sequence.   
     
     
         3 . The starting method of a brushless motor according to  claim 1 , wherein
 when the specific case is a case where the magnetic flux monitored by first energization changes to the positive side and in mid-course further changes to the negative side, the first energization is immediately stopped and switched to second energization.   
     
     
         4 . The starting method of the brushless motor according to  claim 1 , wherein
 when the specific case is a case where the magnetic flux monitored by first energization remains unchanged, changes to the negative side by second energization and in mid-course further changes to the positive side, the second energization is immediately stopped and switched to third energization.   
     
     
         5 . The starting method of the brushless motor according to  claim 1 , wherein
 when the specific case is a case where the magnetic flux monitored by first energization changes to the negative side, further changes to the negative side by second energization but does not change to the positive side in mid-course, the energization is switched to third energization in accordance with the predetermined energizing sequence.   
     
     
         6 . The starting method of a brushless motor according to  claim 1 , wherein
 when the magnetic flux monitored is unchanged during each energization, energization is continued in the predetermined energizing sequence until the magnetic flux monitored changes.   
     
     
         7 . The starting method of a brushless motor according to  claim 2 , wherein
 when the magnetic flux monitored is unchanged during each energization, energization is continued in the predetermined energizing sequence until the magnetic flux monitored changes.   
     
     
         8 . The starting method of a brushless motor according to  claim 3 , wherein
 when the magnetic flux monitored is unchanged during each energization, energization is continued in the predetermined energizing sequence until the magnetic flux monitored changes.   
     
     
         9 . The starting method of a brushless motor according to  claim 4 , wherein
 when the magnetic flux monitored is unchanged during each energization, energization is continued in the predetermined energizing sequence until the magnetic flux monitored changes.   
     
     
         10 . The starting method of a brushless motor according to  claim 5 , wherein
 when the magnetic flux monitored is unchanged during each energization, energization is continued in the predetermined energizing sequence until the magnetic flux monitored changes.   
     
     
         11 . A control device of a three-phase four-pole sensorless brushless motor including a stator having three-phase coils and a four-pole magnet rotor provided in correspondence with the stator, the device comprising:
 a control circuit adapted to energize any two-phase coils of the three-phase coils in a predetermined energizing sequence for starting of the brushless motor; monitor magnetic flux generated in the other one-phase coil; and switch energization to the two-phase coils according to a specific case where the monitored magnetic flux changes to a positive or negative side and in mid-course further changes to an opposite side.   
     
     
         12 . The starting method of a brushless motor according to  claim 11 , wherein
 when the specific case is a case where the magnetic flux monitored by first energization changes to the negative side and in mid-course changes to the positive side, the control circuit immediately stops the first energization and switches the energization to sixth energization by skipping four energizations in the predetermined energizing sequence.   
     
     
         13 . The starting method of a brushless motor according to  claim 11 , wherein
 when the specific case is a case where the magnetic flux monitored by first energization changes to the positive side and in mid course further changes to the negative side, the control circuit immediately stops the first energization and switches the energization to second energization.   
     
     
         14 . The starting method of a brushless motor according to  claim 11 , wherein
 when the specific case is a case where the magnetic flux monitored by first energization changes to the positive side, and further changes to the negative side by second energization and in mid-course further changes to the positive side, the control circuit immediately stops the second energization and switches the energization to third energization.   
     
     
         15 . The starting method of a brushless motor according to  claim 11 , wherein
 when the specific case is a case where the magnetic flux monitored by first energization changes to the negative side, and further changes to the negative side by second energization but does not change to the positive side in mid-course, the control circuit switches the energization to third energization in accordance with the predetermined energizing sequence.   
     
     
         16 . The starting method of a brushless motor according to  claim 11 , wherein
 when the magnetic flux monitored during is unchanged each energization, the control circuit continues the energization in the predetermined sequence until the magnetic flux monitored changes.   
     
     
         17 . The starting method of a brushless motor according to  claim 12 , wherein
 when the magnetic flux monitored during is unchanged each energization, the control circuit continues the energization in the predetermined sequence until the magnetic flux monitored changes.   
     
     
         18 . The starting method of a brushless motor according to  claim 13 , wherein
 when the magnetic flux monitored during is unchanged each energization, the control circuit continues the energization in the predetermined sequence until the magnetic flux monitored changes.   
     
     
         19 . The starting method of a brushless motor according to claim  14 , wherein
 when the magnetic flux monitored during is unchanged each energization, the control circuit continues the energization in the predetermined sequence until the magnetic flux monitored changes.   
     
     
         20 . The starting method of a brushless motor according to  claim 15 , wherein
 when the magnetic flux monitored during is unchanged each energization, the control circuit continues the energization in the predetermined sequence until the magnetic flux monitored changes.   
     
     
         21 . A control device of a brushless motor including a stator having multiple-phase coils and a magnet rotor provided in correspondence with the stator, the device being arranged to: perform forced drive that forcibly energizes each phase coil by sequentially switching energization to each phase coil to rotate the magnet rotor; detect a position of the magnet rotor based on back-EMF voltage generated in each phase coil; and perform back-EMF drive for controlling energization to each phase coil based on a detected position, wherein
 the device comprises a control circuit arranged to: first start the forced drive for starting of the brushless motor; perform the back-EMF drive when the position of the magnet rotor is detected based on the back-EMF voltage within a predetermined time from the start of the forced drive; stop the forced drive when the position of the magnet rotor is not detected based on the back-EMF voltage within the predetermined time from the start of the forced drive; and execute initial setting for controlling energization to each phase coil in order to set the magnet rotor in a initial position that facilitates the starting of the magnet rotor.